The greatest need for ministers and preachers of the Gospel

What is the greatest need for those who preach the gospel? What is the essential foundation for gospel ministry?

Richard Baxter, in his classic, 'The Reformed Pastor' says the greatest need is for the preacher or minister to experience the saving work of God's grace in his own soul.

See that the work of saving grace be thoroughly wrought in your own souls. Take heed to yourselves, lest you be void of that      saving grace of God which you offer to others, and be strangers to the effectual working of that gospel which you preach;      and lest, while you proclaim to the world the necessity of a Savior, your own hearts should neglect him, and you should miss      of an interest in him and his saving benefits. Take heed to yourselves, lest you perish,      while you call upon others to take heed of perishing; and lest you famish yourselves while you prepare food for them. Though      there is a promise of shining as the stars, to those ‘who turn many to righteousness,’ that is but on supposition that they      are first turned to it themselves. Their own sincerity in the faith is the condition of their glory, simply considered, though      their great ministerial labors may be a condition of the promise of their greater glory. Many have warned others that they      come not to that place of torment, while yet they hastened to it themselves: many a preacher is now in hell, who hath a hundred      times called upon his hearers to use the utmost care and diligence to escape it. Can any reasonable man imagine that God should      save men for offering salvation to others, while they refuse it themselves; and for telling others those truths which they      themselves neglect and abuse? Many a tailor goes in rags, that maketh costly clothes for others; and many a cook      scarcely licks his fingers, when he hath dressed for others the most costly dishes. Believe it, brethren, God never saved      any man for being a preacher, nor because he was an able preacher; but because he was a justified, sanctified man, and consequently      faithful in his Master’s work. Take heed, therefore, to ourselves first, that you be that which you persuade your hearers      to be, and believe that which you persuade them to believe, and heartily entertain that Savior whom you offer to them. He      that bade you love your neighbors as yourselves, did imply that you should love yourselves, and not hate and destroy yourselves  and them.  

http://www.ccel.org/ccel/baxter/pastor.ii.i.html